System comprising a refrigerator intended for fractionating gas mixtures



May 3, 1960 J. A. 1.. IJZER 2,934,909

SYSTEM COMPRISING A REFRIGERATOR INTENDED FOR FRACTIONATING GAS MIXTURES Filed Oct. 20, 1955 United States Patent SYSTEM COMPRISING A REFRIGERATOR IN- TENDgD FOR FRACTIONATING GAS MIX- TURE Jacobus Albertns Louisa Ijzer, Eindhoven, Netherlands, assignor, by mesne assignments, to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Application October 20, 1955, Serial No. 541,783

Claims priority, application Netherlands November 3, 1954 2 Claims. (Cl. 62-40) The invention relates to a system for fractionating gas mixtures, this system comprising a cold-gas refrigerator. A known system of this kind comprises a gas fractionating column, the fraction of the lowest boiling point escaping from the column being condensed by means of a cold-gas refrigerator. Part of the condensate is supplied to the column as a washing liquid and a further part is withdrawn from the system as the desired product.

The term cold-gas refrigerator is to be understood to mean herein a refrigerator operating on the reversed hotgas engine principle. Such machines have at least two spaces, the volumes of which are varied by means of piston-like bodies. These spaces of variable volumes communicate with one another via a first heat exchanger, a regenerator and a second heat exchanger. In the working space of the machine, constituted by the spaces of variable volume, the heat exchangers and the regenerator, a gas which is always in the same state of aggregation performs a closed, thermodynamic cycle. In one heatexchanger, called the freezer, heat is supplied to the gas, this heat being withdrawn from the medium to be cooled. In the other heat-exchanger, termed the cooler, heat is withdrawn from the gas by means of a cooling medium, for example water or air.

The gas employed in these machines is often air, hydro gen or helium in accordance with the temperature at which the refrigerator has to' produce cold.

It is known that these refrigerators may be constructed in various ways, for example, as a displacer machine, as a double-acting machine, as a machine, the cylinders of which are at an angle to one another, or as a machine, the working space of which is combined with that of a hot-gas engine.

The invention is based on the recognition of the fact that the refrigerator may be employed successfully also with other systems for fractionating gas mixtures.

In accordance with the invention the system is provided with a heat-exchanger constructed in the form of a dephlegmator, in which the gas mixture is separated into fractions, heat being withdrawn from this heat exchanger by means of the cold-gas refrigerator.

A dephlegmator is to be understood to mean herein a heat exchanger having a wall from which heat is withdrawn so that the gas mixtures condensates partly, the condensate produced being in contact with the gas mixture supplied.

In one embodiment of the invention a simple construction is obtained, if the freezer of the refrigerator is constructed in the form of a dephlegmator.

According to a further aspect of the invention the heat exchanger is in thermal contact via a heat-conducting intermediate agent with the refrigerator. The heat-conducting intermediate agent may, for example, be nitrogen.

According to a further aspect of the invention the heat is withdrawn from the heat exchanger mainly from the colder side thereof.

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If, in accordance with a further aspect of the invention, the heat exchanger is provided with a heat-conducting element, which is connected to the head of the cold-gas refrigerator, the heat may be conducted directly from this element to the cold-gas refrigerator.

If the system comprises a dephlegmator, in which air is separated into fractions, a liquidwill be obtained which is a mixture of about 50% of oxygen and about 50% of nitrogen, while, moreover, substantially pure nitrogen is left as a gas. In accordance with the invention the liquid can then be separated into purer fractions in a gas fractionating column. Use may, in this case, be made successfully of a column of very simple construction.

According to a further aspect 'of the invention the gas fractionating column is constructed as a semi-column. The term semi-column is to be understood to mean herein a column, in whichthe gas mixture to be fractionated is supplied to the column at the top and one of the fractions is withdrawn from the top.

If use is made of the aforesaid column a gas mixture escapes at the top, this mixture containing yet a certain quantity of a component having the higher boiling point. According to one aspect of the invention the fraction escaping from the top of the column is supplied again to the dephlegmator.

The system according to the invention may be used successfully for fractionating gas mixtures differing from air. It is very important that the boiling points of the components should be comparatively different. Thesysterm may, for example, be used to obtain hydrogen from lighting gas.

The invention will be described more fully with reference to two embodiments.

Fig. 1 shows a system, in which the dephlegmator is in thermal contact directly with the head of the cold-gas refrigerator, the liquid produced being separated into further fractions by means of a half column.

According to Fig. 2 the dephlegmator is arranged at a certain distance from the refrigerator as by means of a heat-conducting intermediate agent and heat is withdrawn from the dephlegmator.

Fig. 1 shows a system comprising a cold-gas refrigerator 1. This cold-gas refrigerator comprises a cylinder 2, in which a displacer 3 and a piston 4 move up and down with a substantially constant phase difference. To this end the displacer 3 is coupled by way of connecting rod mechanism 5 with a crank of a crank shaft 6, while the piston 4 is coupled via a connecting rod mechanism 7 with a further crank of the same crank shaft. The coldgas refrigerator is driven by means of a motor, for example an electric motor 8. The displacer 3 acts upon the volume of a space 9, which communicates with a space 13 via a first heat exchanger 10, a regenerator 11 and a second heat exchanger 12.. In the refrigerator a gasmedium performs a closed, thermodynamic cycle, this medium being always in the same state of aggregation. The medium may, for example, be air or, if very low temperatures must be attained, hydrogen or helium. In the present case, in which the refrigerator is to operate at about 187, use may be made of hydrogen. The space 9 is the space of low temperature and the first heat ex-' changer 10 has also a low temperature is generally termed the freezer. The heat exchanger 12 is generally termed the cooler and the space 13 is the space of higher temperature. On the outer side the freezer is provided with vanes 14, located in the condenser space 15. The head of the cold-gas refrigerator comprises an element 16 of a material of good thermal conductivity, which is connected at the top for heat conduction to a cylinder 17, which is provided with vanes 18 extending in a vertical direction. The condenser space has a supply duct 19, which is connected a heat exchanger 20. This heat ex- 3 changer 20 is located in a boiler 21 of a semi-column 22. The heat exchanger 20 communicates with a duct 23, which comprises a heat exchanger 24. The cylinder 17 with the vanes 18 serves as a dephlegmator in which the gas mixture to be fractionated, in this case for example air, is separated into fractions. Thus, at the top of the dephlegmator substantially pure nitrogen is produced and at the bottom is produced a liquid rich in oxygen. If the conditions are favourable, this liquid will contain about 50% of oxygen. The nitrogen produced in the dephlegmator is withdrawn from the system via a duct 25, which communicates with the heat exchanger 24 and which has, furthermore, a ventilator 26.

' The liquid produced in the dephlegmator is conducted via a duct 27 at the top into the column 22. This column may be filled up with filling material, for example saddles or Raschig rings. The column may, as an alternative, contain dishes. In the column the liquid rich in oxygen is separated further into fractions, a gas mixture rich in nitrogen being thus collected at the top of the column. This gas mixture rich in nitrogen may be conducted to the heat exchanger 24 via the duct 28, in order to cool the air to be fractionated together with the nitrogen produced in the dephlegmator, or it may be conducted to the coldgas refrigerator via a duct 29 and the duct 19, in order to be fractionated in the dephlegmator. The outlet duct 28 has a ventilator 30, which is capable of sucking the gas mixture out of the column.

Fig. 2 shows the outer side of a cold-gas refrigerator 31. This machine, as the machine shown in the preceding figure, may be constructed in the form of a displacer machine. However, as an alternative, a different type of cold-gas refrigerator, for example, a double-acting machine, having, consequently, a plurality of cylinders arranged side by side, may be used. The refrigerator com- 4 dephlegmator has an outlet duct 44 with a ventilator 45. The gas mixture supplied to the dephlegmator is separated herein into fractions. If, for example, lighting gas is fractionated to obtain hydrogen, a liquid is produced, which contains mainly COCH this liquid is withdrawn from the dephlegmator at the bottom. At the top hydrogen is collected and conducted away through the duct 44.

prises a condenser space 32, provided with an outlet duct 33. This outlet duct communicates with a space 34 and from this space via a duct 35 again with the cold-gas refrigerator. The duct 33 has a liquid pump 36. In the duct system described above can circulate a heatconducting intermediate agent, for example nitrogen. This nitrogen is condensed in the condenser space 32 and the liquid thus produced is transported by means of the pump 36 to the space 34, in which the liquid evaporates and the gas produced flows back to the refrigerator through the duct 35. The space 34 has, at the bottom, a tube 37, which is provided externally with vanes 38 extending in a vertical direction, the tube being surrounded by a tube 39. At the bottom of the heat exchanger thus constructed, which is capable of operating as a dephlegmator, provision is made of a collecting space 40 for the liquid produced, this space having an outlet duct 41 and a liquid trap 42, while provision is made of an inlet duct 43 for the gas mixture to be fractionated. At the top the What is claimed is:

l. A gas fractionating system comprising a column, a cold gas refrigerator, conduit means interconnecting said column and cold gas refrigerator, said cold gas refrigerator being provided with a freezer, regenerator and cooler, and having a medium therein performing a closed thermodynamic cycle through said freezer, regenerator and cooler, and a dephlegmator having a gas mixture therein operatively connected to said freezer whereby heat is withdrawn from said dephlegmator by means of said freezer thereby condensing at least part of said gas mixture, means drawing off the gaseous fraction of said mixture from the top of said dephlegmator, and means for supplying the fraction escaping from the top of said column to said dephlegmator.

2. A gas fractionating system comprising a column, a cold gas refrigerator, conduit means interconnecting said column and cold gas refrigerator, said cold gas refrigerator being provided with a freezer, regenerator and cooler, and having a medium therein performing a closed thermodynamic cycle through said freezer, regenerator and cooler, and a dephlegmator having a gas mixture therein operatively connected to said freezer whereby heat is withdrawn from said dephlegmator by means of said freezer thereby condensing at least part of said gas mixture, means drawing off the gaseous fraction of said mixture from the top of said dephlegmator, and means for selectively conducting the fraction escaping from the top of the said column to the atmosphere or back to said dephlegmator.

References Cited in the file of this patent UNITED STATES PATENTS 1,730,580 Lundgaard Oct. 8, 1929 2,113,680 De Baufre Apr. 12, 1938 2,287,137 Ross June 23, 1942 2,408,710 Van Nuys Oct. 1, 1946 2,458,894 Collins Jan. 11, 1949 2,525,660 Fausek Oct. 10, 1950 2,626,510 Schilling Ian. 27, 1953 2,734,354 Kohler Feb. 14, 1956 FOREIGN PATENTS 154,490 Australia Dec. 10, 1953 520,564 Belgium Dec. 9, 1953 699,262 Great Britain Nov. 4, 1953 

1. A GAS FRACTIONATING SYSTEM COMPRISING A COLUMN, A COLD GAS REFRIGERATOR, CONDUIT MEANS INTERCONNECTING SAID COLUMN AND COLD GAS REFRIGERATOR, SAID COLD GAS REFRIGERATOR BEING PROVIDED WITH A FREEZER, REGENERATOR AND COOLER, AND HAVING A MEDIUM THEREIN PERFORMING A CLOSED THERMODYNAMIC CYCLE THROUGH SAID FREEZER, REGENERATOR AND COOLER, AND A DEPHLEGMATOR HAVING A GAS MIXTURE THEREIN OPERATIVELY CONNECTED TO SAID FREEZER WHEREBY HEAT IS WITHDRAWN FROM SAID DEPHLEGMATOR BY MEANS OF SAID FREEZER THEREBY CONDENSING AT LEAST PART OF SAID GAS MIXTURE, MEANS DRAWING OFF THE GASEOUS FRACTION OF SAID MIXTURE FROM THE TOP OF SAID DEPHLEGMATOR, AND MEANS FOR SUPPLYING THE FRACTION ESCAPING FROM THE TOP OF SAID COLUMN TO SAID DEPHLEGMATOR. 